MEMS microphone are widely used in mobile terminals, such as mobile phones, tablet computers, laptop computers, portable game players, portable multimedia devices, or the like, and serve as a sound pickup device for converting the sound into an electrical signal.
A MEMS microphone chip includes a vibration membrane and a back plate bonded to each other for forming a MEMS acoustic sensing capacitor. The vibration membrane includes a membrane connecting pad, and the back plate includes a back plate connecting pad; the membrane connecting pad and the back plate connecting pad are provided to output an acoustic sensing signal generated by the MEMS microphone chip to a signal processing chip.
The membrane connecting pad and the back plate connecting pad are generally formed in the MEMS microphone chip by using a shadow mask. The shadow mask provides two openings respectively for depositing the membrane connecting pad and the back plate connecting pad. Each of the membrane connecting pad and the back plate connecting pad normally has a small size, e.g., 100 μm×100 μm; therefore, in a related shadow mask, the opening is designed to have an inverted cone structure with a large top opening area, e.g., 460 μm×460 μm. However, the large top opening area of the opening makes it difficult to form multiple openings in the vibration membrane or the back plate, and moreover, the large top opening area may also lower an alignment accuracy between the shadow mask and the MEMS microphone chip.
Therefore, it is desired to provide a photographic mask and a method for making the photographic mask which can overcome the aforesaid problems.